Patent Document 1 discloses a testing device for a transmission of a vehicle used in a production line and others. In the transmission testing device disclosed in Patent Document 1, the transmission is connected to an input shaft for applying input rotation to the transmission and connected to two output shafts corresponding to left and right driving wheels. In the transmission testing device of Patent Document 1, the input rotation is applied to the transmission by a direct current motor via the input shaft to thereby carry out various tests on the transmission.